The present invention relates to an apparatus for producing special television effects, and more particularly to a chromakey effect apparatus.
The chromakey effect apparatus works to insert a picture by utilizing the difference in hue of color signals. So far, however, an unnatural appearance developed at the border of the inserted picture. A chromakey generating apparatus which is free from the abovementioned defect was announced in the SMPTE's 121st Technical Conference held in Los Angeles on Oct. 22, 1979, and has been disclosed in an SMPTE journal articles, "High Quality Montage Pictures by a New Color Killer Soft Chromakey System", Vol. 90, February, 1981, pages 107-112. According to this apparatus, the objects are achieved by utilizing a linear gate and by employing a color killer circuit.
The prior art chromakey apparatus disclosed in the above-mentioned article consists of a chromakey signal generating unit, a soft chromakey signal generating unit, and a color killing unit. The color killing unit produces a color killing subcarrier for cancelling the color of a portion in which another picture will be inserted. In the color killing unit of the prior art shown in FIG. 7 of the above-mentioned article, the phase and amplitude information corresponding to the hue and saturation of a chromakey area, for example, a chromakey area, are memorized in the memories, respectively, and the color killing signal is produced in response to the phase and amplitude information stored in the memories. In this case, the particular portion of the chromakey area is specified by a window gate signal in order to memorize the phase and amplitude information. Therefore, when the saturation or hue of the chromakey area is changed, the color will not be killed completely unless the phase and amplitude information are re-sampled and stored again in the memories, and it becomes difficult to obtain chromakey effect of good quality. This means that a limitation is imposed on the ranges for moving key cameras.
Further, although the hue and saturation of the chromakey area portion can be changed in order to convert the color by utilizing the color killing function, it is difficult to kill the color and to convert the color simultaneously at different portions respectively.
If, outside of the chromakey area portion, a portion having the same color of the chromakey area is contained in the TV picture, that portion, which is not to be chromakeyed, would be chromakeyed. Therefore, if a person wearing blue clothing stands in front of the chromakey area, the other picture is inserted into the chromakey area as well as the portion corresponding to the blue clothing. Consequently the person is not allowed to wear blue clothing or a blue necktie.
Furthermore, when the chromakey area portion is small, the chromakey effect cannot be effected up to the outer side of the chromakey area. Moreover, the chromakey effect cannot be effected perfectly when characters of other colors are contained in the chromakey area.
A first object of the present invention, therefore, is to provide a chromakey effect apparatus which is capable of reliably killing color even when the hue or saturation of the chromakey area is changed.
A second object of the present invention is to provide a chromakey effect apparatus which kills the color while simultaneously converting the color, in order to obtain effects that are not found in the prior art.
A third object of the present invention is to provide a chromakey effect apparatus which is capable of reliably chromakeying only the chromakey area even when there are many portions having the same color as the chromakey area.
A fourth object of the present invention is to provide a chromakey effect apparatus which is capable of reliably chromakeying a desired portion even when the desired portion includes a part having different colors.
A fifth object of the present invention is to provide a chromakey effect apparatus which is capable of producing a monitor picture signal which indicates a region to be effected.
According to the present invention, there is provided a color killing subcarrier generating circuit which is capable of canceling the color of the chromakey area completely even when the hue or saturation of the chromakey area is changed. The color killing subcarrier generating circuit of the invention comprises means for extracting the subcarrier from the television signal containing the chromakey area, means for receiving a reference subcarrier and for shifting the phase of the reference subcarrier in response to a phase control voltage, gain control means for controlling the amplitude of the reference subcarrier delivered from said phase shifting means in response to a gain control voltage, phase comparator means for comparing the phase of the subcarrier delivered from said extracting means with the phase of the reference subcarrier delivered from said phase shifting means, first supplying means for supplying the compared result to said phase shifting means as said phase control voltage, means for comparing the amplitude of the subcarrier delivered from said extracting means with the amplitude of the reference subcarrier delivered from said phase shifting means, and second supplying means for supplying the compared result of said comparing means to said gain control means as said gain control voltage.
Further, according to another aspect of the present invention, there is provided a chromakey effect apparatus which is capable of inserting another television signal into only a desired portion of the chromakey area and of converting the color of the remaining portion of the chromakey area. The chromakey effect apparatus comprises an area signal generating circuit to restrict a portion to be chromakeyed and a color conversion circuit.